1. Field of the Invention
The present invention relates to plasma display devices generally and, more particularly, but not by way of limitation, to a novel plasma display panel which is very economically manufactured and which has increased luminous efficiency and color purity.
2. Background Art
There is a great deal of interest in plasma display panels because such display devices consume far less space in the direction normal to the plane of the picture as compared to conventional cathode ray tubes. While the use of cathode ray tubes as display devices is quite widespread, they suffer from a number of other defects or undesirable features. Cathode ray tubes have a poor small area contrast ratio due to light scattering and a further phenomenon called "halo." When an electron beam impinges on a phosphor surface, that surface radiates light forwardly toward an observer, but light is also radiated inwardly, reflected and radiated back outwardly to form a bright donut or halo spaced around the central spot. This effectively enlarges the visible spot with consequent loss of perceived detail. Present day plasmas display technologies have somewhat similar problems which reduce resolution.
The basic theory of operation of alternating current plasma displays may be found in a number of sources such as U.S. Pat. Nos. 3,559,190; 3,935,494; and 4,233,623, as well as in an article by T. N. Criscimagna and P. Pleshko titled AC PLASMA DISPLAY found in Applied Physics, Vol. 40, published by Springer Verlag in 1980, the disclosures of which patents and article are incorporated by reference hereinto.
Briefly, such display devices have a plurality of gas discharge cells arranged in a generally flat matrix, and first and second sets of spaced apart electrodes with each cell located intermediate one electrode of the first set and one electrode of the second set. The display panel is formed with a first generally flat dielectric plate having the first set of electrodes therein, a second generally flat dielectric having the second set of electrodes therein, and with the two plates sealed together about their common periphery to enclose a gas such as a neon-argon mixture. Light emission is caused either by stimulation of such a visibly luminous gas mixture or by stimulation of phosphors within the cell. Phosphors responsive to ultraviolet radiation created by a discharge in a cell through the enclosed gas are coated on the one of the two plates through which the display is viewed or the selected gas may be one such as a neon-xenon mixture which has significant radiation in the visible spectrum in which case the phosphors may be eliminated.
In such known display devices, a gas discharge in one cell may energize the phosphors associated with one or more adjacent cells, resulting in a larger than desired basic picture element and a resultant loss of color purity. Attempts have been made to eliminate this "cross-talk" between adjacent cells by providing an intermediate layer in the form of a perforated plate having individual holes corresponding to individual cells. This attempt creates problems in evacuating the display device and refilling it with the desired gas and further eliminates the desired phenomenon of "priming" wherein some intercellular photon or charged particle migration reduces the voltage necessary to fire or energize a cell. Further attempts to isolate cells and eliminate cross-talk while retaining the priming feature and allowing charging of the display device with the proper gas mixture have included a zigzag pattern of passageways between cells (U.S. Pat. No. 3,869,630), an orthogonal array of grooves or troughs (U.S. Pat. No. 3,953,756), and dielectric glass spacing bosses separating the cells (U.S. Pat. No. 4,827,186. None of these is entirely satisfactory and all are relatively expensive to manufacture.
Accordingly, it is a principal object of the present invention to provide a plasma display panel which is economical to manufacture.
It is a further object of the invention to provide such a plasma display panel which provides increased luminous efficiency and color purity.
Other objects of the present invention, as well as particular features, elements, and advantages thereof, will be elucidated in, or be apparent from, the following description and the accompanying drawing figures.